Our overall and long continuing interest is in the role of the autonomic system in relating somatic and endocrine control systems. Our currently proposed work will be in 1) the study of cardiac reflexes: a) the integrated participation of both para- and sympathetic controls will be studied; b) contribution of supramedullary structure to the reflex will be investigated and particular attention will be paid to hypothalamic control because this probably plays a major role in producing both totality of response and a differential control of autonomic system activity; c) mechanism of action of mechanoreceptors in atria as a volume receptor controlling urine output. This is still a controversial subject but the reactions reported are likely to involve neuroendocrine cells in the hypothalamus. 2) Influence of light and control by the suprachiasmatic nucleus of sympathetic activity; the relationship of the optic system and this nucleus to circadian changes in autonomic activity. 3) Autonomic control of the pineal - more detailed analysis of its mechanism and its functional significance.